The manufacturing of integrated circuits often involves the bonding of device dies to package substrates. In a typical bonding process, a device die is first picked up from a wafer that has already been sawed into dies. The device die is flipped upside down and placed on a table. A bond head then picks up the flipped device die from the table, and then places the device die on a package substrate. After a plurality of devices dies are placed on a plurality of package substrate of a package substrate strip, the package substrate strip along with the device dies go through a reflow process, so that the device dies are bonded to the package substrates.
The accuracy in the placement of the device die on the package substrate needs to be well controlled to maintain the yield of the bonding process. On the other hand, the throughput of the pick-and-place process also needs to be improved. However, the requirement in the accuracy of the placement conflicts with the requirement of the increasing the throughput. For example, to improve the throughput, the moving speed of the bond head needs to be increased. However, the increased moving speed results in the sacrifice in the accuracy of the placement. Although multiple bond heads may be used for picking and placing the device dies, each of the multiple bond heads needs to wait for the work space used by other bond heads to be cleared before it can be put into work. The improvement in the throughput is thus limited.